Question

Which sentence below uses commas correctly?

On thing that will help you, Katie, is to place all of your assignment due dates in
a planner, or on a calendar.

On thing that will help you, Katie, is to place all of your assignment due dates in
a planner or on a calendar.

None of these sentences are correctly punctuated.

On thing that will help you Katie is to place all of your assignment due dates in a
planner or on a calendar.

Answer 1

The first option,

One thing that will help you, Katie, is to place all of your assignment due dates in  a planner, or on a calendar.

Answer 2

Answer:

The second one

Explanation:

There is no need to add a comma after 'a planner' in the first one. One thing that always helps when answering these types of questions is to read the sentence aloud and think about whether it makes sense or not. If not, it is likely an incorrect use of punctuation. Another thing you can do is by someone reading the sentence with no commas, and then asking you to write it out without looking, but by adding commas where you think is right. Then, read that aloud and try to determine whether it is fluently-read.

However, going back to the question, I think it's meant to say 'one' instead of 'on' in the beginning of both sentences.